Duplex directive antenna system



y 1951 B. P. BROWN, JR 2,552,146

DUPLEX DIRECTIVE ANTENNA SYSTEM Filed May 8, 1948 Inventor: Burton P Brown Jr.

b m; AM

His Attorney.

Patented May 8, 1951 DUPLEX DIRECTIVE ANTENNA SYSTEM Burton P. Brown, Jr.,

signor to General El ration of New York Baldwinsville, N. Y., asectric Company, a corpo- Application May 8, 1948, Serial No. 25,897

6 Claims. (01. 250-33.65)

This invention relates to a unitary antenna system utilizing two trains of plane polarized electromagnetic waves, mutually perpendicular to each other in the plane at right angles to their direction of propagation and capable of providing simultaneous operation of radio apparatus on the same or on closely adjacent frequencies.

It is an object of this invention to provide an improved antenna structure for simultaneous transmission and reception on the same or on closely adjacent frequencies. 7

Another object of this invention is to provide a new and improved antenna mount and feed assembly for two mutually perpendicular dipoles so that the dipoles may be independently excited and yet electrically decoupled from each other.

A further object of this invention is to provide an improved means for mounting a reflecting plate in front of the two mutually perpendicular dipoles of such a duplex antenna system, in such a way that in conjunction with a concave reflector, said reflecting plate will conserve the direct forward radiation and yet not disturb the electrical decoupling of the two dipoles.

For additional objects and advantages and for a better understanding of the invention, attention is now directed to the following description and accompanying drawings, and also to the appended claims in which the features of the invention believed to be novel are particularly pointed out. In the drawings:

Fig. l is a longitudinal sectional view of a duplex directive antenna system embodying the invention, and Fig. 2 is a partial sectional view in the plane AA in Fig. 1 and looking in the direction of the two arrows. The capital letters A, B, C, D, E, F, G and H refer to plane sections through the assembly at the positions indicated by the adjacent section lines.

Referring to the drawings, the system comprises a concave reflector i which may be a paraboloid in form. The vertical dipole antenna consists of members 2 and 3 while the horizontal dipole antenna consists of members 4 and 5 and the one is mounted at 90 with respect to the other. The dipole members may consist of flat plates with rounded ends as shown.

A co-axial transmission line I, 8 enters the assembly at section B and feeds the vertical dipole 2, 3. A similar co-axial transmission line 9, It] has an expanding conical cross section from section D to section E for improved matching purposes and enters the main assembly at section C, where conductor 9 is fastened to conductor 8. The coaxial transmission lines '1, 8 and 9, l0 are adapted to be energized from two separate sources of high frequency energy which may be of the same or different frequencies. The invention has particular utility in a system where the antennas are to be energized at the same, or

closely adjacent, high frequencies, where it is most difficult to avoid undesired mutual coupling. Section B to C of tubular conductor l2 provides a quarter-wavelength metallic insulator to secure the assembly, the quarter wavelength being with respect to the frequency impressed between conductors 9 and I8.

At section F, a tubular shell [4 is fastened to the outside of tubular conductor I2 which is there terminated in an expanding conical cross section. Also at section F, a conducting cone i5 is fastened to conductor 8 and at section G an intermediate tubular shell I3 is fastened to the conducting cone I5. The purpose of the conical cross section of tubular conductor l2 and of cone I5 is to provide an impedance match between the co-axial system consisting of conductors l2 and 8 and the system consisting of shells l3 and [4.

Two slots 26 are formed by cutting conductor 8 on both sides in parallel horizontal planes for a length of approximately one-quarter wavelength at the operating frequency of the dipole 2, 3, on either side of section line A and extending from section H to section G. At section A, inner conductor 1 is fastened by a short vertical conductor 25 to either the upper or lower segment of conductor 8. In this embodiment the upper segment of conductor 8 is the one connected.

Two short slots 2'! are formed by cutting shell is on both sides in parallel vertical planes for a length suificient to insure the projection of dipole elements 2 and 3 through the shell without contact. Two slots 28 are formed by cutting shell E4 on both sides in parallel vertical planes for a length of approximately one-quarter wavelength,

at the operating frequency of dipole 4, 5, on either side of section A and extending from section H to section G. At section A, horizontal dipole elements 4 and 5 are fastened to shell l4, and one of the elements, in this embodiment the righthand element 4 as shown in Fig. 2, projects right through shell M and is also fastened to shell I3.

At section H, the conducting assembly, consisting of conductor 8 and shells l3 and M, is terminated by a bushing 38. Circular reflector 3| is fastened to the bushing 38 and is placed at a distance from section A through the dipole elements of approximately one-quarter wavelength at the mean operating frequency of the dipoles.

In operation, the effect of the quarter-wave portion of the slots 26 from section G to section A is to make a balancing transformer of the uncut sections of conductor 8 which convert the balanced impedance of the dipole elements 2 and 3 into the characteristic impedance of inner conductor I to conductor 8. Similarly the effect of the portion of the slots 28 from section G to section A is to make a balancing transformer of the uncut section of shell I4 which converts the balanced impedance of the dipole elements 4 and 5 into the characteristic impedance of shell 13 to shell l4. The short slots 21 in shell I3 are simply to permit mounting of the vertical dipole elements 2 and 3 independently of shell I3. The purpose of the quarter-wave portions of slots 26 and 28, from section A to section H, is to effect a metallic insulator to provide a more balanced and decoupled electric field and to give mechani-- cal support to reflector 3|.

It will be observed that to the right of section F, the radio frequency excitation to dipole elements 2 and 3 is by means of the electromagnetic field existing between conductors 1 and 8, and similarly, the radio frequency excitation to dipole elements 4 and 5 is by means of the electromagnetic field existing between conductor 8 and tubular conductor I2. From section F to G, the impedance is converted and to the left of section G, the excitation for dipole elements 2 and 3 remains unchanged by means of the electromagnetic field between conductors I and 8, while the excitation to dipole elements 4 and 5 is now by means of the electromagnetic field existing between shells I3 and Hi. The purpose of this arrangement is to decouple the vertical dipole elements from the horizontal dipole elements and prevent any coupling in the feed system.

While a specific embodiment has been shown and described, it will, of course, be understood that various modifications may be made without departing from the invention. The appended claims are therefore intended to cover any such modifications within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A duplex directive antenna system for simultaneous operation with two independent radio frequency waves of the same or closely adjacent high frequencies, comprising a' pair of mutually perpendicular dipole antennas lying in a plane normal to the directive axis of the system, each dipole antenna having a pair of center feed points, a coaxial structure comprising an in ner conductor extending along said axis and surrounded by an intermediate coaxial tubular conductor and by an outer coaxial tubular conductor, said structure terminating at a distance from said plane substantially equal to one quarter wavelength at the mean operating frequency of said antennas, first coupling means for supplyin wave energy to the first channel defined by said inner and intermediate conductors, second coupling means for supplying Wave energy to the second channel defined by said intermediate and outer conductors, and two groups of three substantially parallel line conductors for individually coupling said antennas to said channels, said first group providing a first connection from one feed point of one antenna to the end of said inner conductor, a second connection from said one feed point of said one antenna to the end of said intermediate conductor and a third connection from the other feed point of said one antenna to the end of said intermediate conductor, and said second group providing a fourth connection from one feed point of said other antenna to the end of said intermediate conductor, a fifth connection from said one feed point of said other antenna to the end of said outer conductor and a sixth connection from the other feed point of said other antenna to the end of said outer conductor.

2. A duplex directive antenna system for simultaneously operation with two independent radio frequency waves comprising a pair of mutually perpendicular dipole antennas lying in a plane normal to the directive axis of the system, each dipole antenna having a pair of center feed points, a coaxial structure comprising an inner conductor extending along said axis to said plane and surrounded by an intermediate coaxial tubular conductor and by an outer coaxial tubular conductor, first coupling means for supplying wave energy to the first channel defined by said inner and intermediate conductors, second coupling means for supplying wave energy to the second channel defined by said intermediate and outer conductors, said intermediate and outer conductors each being cut away to define a pair of complementary longitudinal slots opposite a different one of said antennas, the remaining wall portions forming inner and outer pairs of substantially parallel conducting portions, one pair of said conducting portions being connected to the feed points of each antenna, each of said slots extending away from said plane along said axis by a distance substantially equal to a quarter wavelength at the frequency of operation of the antenna connected to the adjacent portions, a first feed connection between said inner conductor and one feed point on the inner pair of said portions, and a second feed connection between said intermediate conductor and one feed point on the outer pair of said portions.

3. A duplex directive antenna system for simultaneous operation with two independent radio frequency waves comprising a pair of mutually perpendicular dipole antennas lying in a plane normal to the directive axis of the system, each dipole antenna having a pair of center feed points, a coaxial structure comprising an inner conductor extending along said axis to said plane and surrounded by an intermediate coaxial tubular conductor and by an outer coaxial tubular conductor, first coupling means for supplying wave energy to the first channel defined by said inner and intermediate conductors, second coupling means for supplying wave energy to the second channel defined by said intermediate and outer conductors, said intermediate and outer conductors being cut away to define a pair of complementary longitudinal slots opposite a different one of said antennas, the remaining walls forming inner and outer pairs of substantially parallel conducting portions, one pair of said conducting portions being connected in said plane to the feed points of each antenna, each of said pairs of slots extending away from said plane along said axis by a distance substantially equal to a quarter wavelength at the frequency of operation of the antenna connected to the respective portions, a first feed connection in said plane between said inner conductor and one feed point on the inner pair of said portions, and a second feed connection between said intermediate conductor and one feed point on the outer pair of said portions, said second feed connection being located at a point spaced one-quarter wavelength from said plane at the frequency of operation of the antenna connected to said outer pair of said portions.

4. A duplex directive antenna system for simultaneous operation with two independent radio frequency waves comprising a pair of mutually perpendicular dipole antennas lying in a plane normal to the directive axis of the system, each dipole antenna having a pair of center feed points, a coaxial structure comprising an inner conductor extending along said axis and surrounded by an intermediate coaxial tubular conductor and by an outer coaxial tubular conductor, first coupling means for supplying wave energy to the first channel defined by said inner and intermediate conductors, a second coupling means for supplying wave energy to the second channel defined by said intermediate and outer conductors, said intermediate and outer conductors each being cut away on both sides of said plane to define a pair of complementary longitudinal slots opposite a different one of said antennas, the remaining walls forming inner and outer pairs of substantially parallel conducting portions, one pair of said conducting portions being connected in said plane to the feed points of each antenna, and said slots each extending away from said plane in both directions along said axis by a distance substantially equal to a quarter wavelength at the frequency of operation of the antenna connected to the respective portions, an intermediate coaxial tubular shell positioned between said pairs of conducting portions, said intermediate shell being connected at one end-to said intermediate conductor and having openings surrounding the antenna connections to said inner pair of portions, a first feed connection in said plane between said inner conductor and one feed point on the inner pair of said portions, a second feed connection in said plane between said intermediate shell and one feed point on the outer pair of said portions, and a reflector conductively supported by said portions and by said shell on the opposite side of said plane from said first and second coupling means.

5. A duplex unidirectional antenna system for simultaneous operation with two independent radio frequency waves comprising a pair of mutually perpendicular dipole antennas lying in a plane normal to the directive axis of the system, each dipole antenna having a pair of center feed points, a coaxial structure comprising an inner conductor extending along said axis and surrounded by an intermediate coaxial tubular conductor and by an outer coaxial tubular conductor, first coupling means for supplying wave energy to the first channel defined by said inner and intermediate conductors, second coupling means for supplying wave energy to the second channel defined by said intermediate and outer conductors, said intermediate and outer conduetors each being cut away on both sides of said plane to define a pair of complementary longitudinal slots opposite a different one of said antennas, the remaining walls forming inner and outer pairs of substantially parallel conducting portions, one pair being connected in said plane to the feed points of each antenna, and said slots each extending away from said plane in both directions along said axis by a distance substantially equal to a quarter wavelength at the frequency of operation of the antenna connected to the respective portions, an intermediate coaxial tubular shell positioned between said pairs of conducting portions, said intermedite shell being connected at one end to said intermediate conductor and having openings surrounding the antenna connections to said inner pair of portions, a first feed connection in said plane between said inner conductor and one feed point on the inner pair of said portions, a second feed connection in said plane between said intermediate shell and one feed point on the outer pair of said portions, and a concave reflector positioned to locate the focus thereof substantially at said antenna.

6. A duplex unidirectional antenna system for simultaneous operation with two independent radio waves on closely adjacent frequencies, comprising a pair of mutually perpendicular dipole antennas lying in a plane normal to the directive axis of the system, each dipole antenna having a pair of center feed points, a coaxial structure comprising an inner conductor extending along said axis and surrounded by an intermediate coaxial tubular conductor and an outer coaxial tubular conductor, first coupling means for supplying wave energy to the first channel defined by said inner and intermediate conductors, second coupling means for supplying wave energy to the second channel defined by said intermediate and outer conductors, said intermediate and outer conductors each being cut away on both sides of said plane to define a pair of complementary longitudinal slots opposite a different one of said antennas, the remaining walls forming inner and outer pairs of substantially parallel conducting portions, one pair being connected in said plane to the feed points of each antenna, and said slots each extending forwardly and also rearwardly from said plane along said axis by distances substantially equal to a quarter wavelength at the mean operating frequency of said antennas, an intermediate coaxial tubular shell positioned between said pairs of conducting portions, said intermediate shell being connected to said intermediated conductor at a distance one quarter wavelength rearwardly of said plane, said shell openings surrounding the antenna connections to said inner pairs of portions, a first feed connection in said plane between said inner conductor and one feed point on the inner pair of said portions, a second feed connections in said plane between said intermediate shell and one feed point on the outer pair of said portions, a transverse reflecting plate conductively supported by said intermediate and outer conductors and by said intermediate shell at a distance approximately one quarter wave-length forwardly of said plane, and a concave reflector surrounding said co-axial structure and located rearwardly of said plane with said dipole antennas near its focal point.

BURTON P. BROWN, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,927,393 Darbord Sept. 19, 1933 2,251,530 Thorne Aug. 5, 1941 2,417,895 Wheeler Mar. 25, 1947 

